Some conventional printers perform a recording operation by feeding recording paper in the direction of the width of the same in a recording section while moving it in a paper feed direction. In particular, when a recording operation is performed on a cut form that is manually fed such as an envelope or cut paper, it is necessary for preferable recording to move the recording paper in a feeding direction such that it is not tilted in the direction of the width thereof. Referring to the prior art, for example, JP-A-1-267075 has disclosed an example in which a plurality of pinch rollers are provided side by side in the direction of the width of paper; means is provided for obtaining a correction amount for a pressure to be applied from each of the pinch rollers to a capstan roller when recording paper is moved in a feeding direction; and a pressure correction controller for controlling the applied pressure based on the correction amount.
For example, according to JP-A-5-155086, a paper feed roller and a separating roller are rotated in a forward direction and an inserter driving roller is rotated in the reverse direction when paper is fed. When the leading edge of the paper is located above a sensor, a control circuit detects that the output of the sensor has been turned on and feeds the paper further by the distance between the sensor and the inserter driving roller plus an overfeed amount. The overfeed amount is set at a great value for thick paper and at a smaller value for thinner paper. In the example disclosed, the inserter driving roller is then rotated in the forward direction to put the paper feed roller and the separating roller in an idle state.
However, in the first example of the prior art, there is a need for special mechanisms, i.e., the means for obtaining correction amounts for respective pressures to be applied by the pinch rollers to the capstan roller and the pressure correction controller for controlling the applied pressures based on the correction amounts, which has resulted in the problem of a cost increase. In the second example of the prior art, when paper is deflected by overfeeding the same, the thickness of the paper and the amount of deflection may not be in an appropriate relationship, and a problem has arisen in such a case in that a tilted state cannot be corrected.
Under such circumstances, the invention provides an apparatus which allows correction to be performed to prevent paper from being fed in a tilted state without a need for any special mechanism.
A printer according to the invention is characterized in that it has head driving means for moving a printing head along a platen in the direction of the width of paper that is orthogonal to a paper feed direction, paper feed means for feeding paper into a gap between said printing head and said platen, paper detecting sensors for detecting the position of the leading edge of said paper in a plurality of positions in the direction of the width of the paper when said paper is fed, a moving mechanism for moving said printing head toward and away from said platen; and gap adjusting means for driving said moving mechanism in the direction in which said printing head moves toward said platen to urge said printing head against said paper and for spacing said printing head from said platen a predetermined amount with said position serving as a reference, thereby adjusting the gap between said printing head and said platen, and skew correcting means for detecting the direction and amount of a tilt of said paper based on signals output by said paper detecting sensors when said the paper is fed and for driving said head driving means and said moving mechanism such that an edge of said paper in the direction of the width thereof is sandwiched between said printing head and said platen when said amount of the tilt exceeds a predetermined range and driving said paper feed means such that the paper is rotated about the sandwiched portion depending on the direction of the tilt, thereby correcting the amount of the tilt such that it stays in the predetermined range. Since the skew correcting means operates by sandwiching paper using the head driving mechanism for moving the printing head along the platen, the moving means for moving the printing head toward and away from the platen, and the gap adjusting means and by rotating the paper with the paper feed means, a tilted state of paper can be easily corrected without a need for any special mechanism other than those of a printer.
Said skew correcting means preferably controls the driving of said head driving means and said paper feed means such that said sandwiched portion is always said edge of the paper in the direction of the width thereof regardless of said direction of tilt and such that said feeding direction of the paper is switched depending on said direction of the tilt.
Said skew correcting means preferably switches the sandwiched portion between the edge of the paper in the direction of the width thereof and another edge of the same depending on said direction of the tilt and controls the driving of said head driving means and the paper feed unit such that the feeding direction of the paper is always a constant direction regardless of said direction of the tilt.
Said paper detecting sensors are preferably disposed in positions in which they face both edges of said paper in the direction of the width thereof. This maximizes the amount of the tilt of the paper to allow accurate correction of a tilted state.